The best way to start would find a way to obtain the cooking skill.
Then get the Poultry Recipe Book (This book is in Calvi), buy chickens and Lisbon.
Use the poultry book to make eggs.
Sell them to the market keeper and then sail to another city and go back and repeat.
After a while your skill should go up.
Then get into making the chicken into poultry or you can buy ducks in Gijon and make duck meat.
Eventually after a while you can head to Porto to buy the Pig Recipe Books.
With this you can make the pigs into pork and the pork into bacon.
After this for a while you can now make sausage.
Eventually you may want the Cattle Recipe Book, so making beef will help you level your skill.
And while leveling up your skill, you can make a good sum of money too.
Another recipe book to get is the Simple recipes one, allowing you to mill wheat.
I don't really suggest it as a way to level up your skill though, as one it can be a slow process and the profit made isn't too high. But Milling is the cheapest and fastest way to lvl up cooking untill level 3.